1. Field of the Invention
The present invention relates to an image processing method and an image processing apparatus capable of performing high-quality image recording with less faint printing and bleeding, having improved durability to repeated printing, being low cost, and exhibiting high processing speed.
2. Description of the Related Art
To date, image recording and image erasing on a thermoreversible recording medium (hereinafter may be referred to as “recording medium”) have been performed in a contact manner where a heat source is brought into contact with a recording medium to heat the recording medium. The heat source used is generally a thermal head for image recording and a heat roller or a ceramic heater for image erasing.
In such contact-type recording method, when the thermoreversible recording medium is flexible one such as a film or paper, a platen is used to uniformly press the heat source against the thermoreversible recording medium, whereby uniform image recording and image erasing can be performed. In addition, conventionally used parts of printers for thermosensitive paper can be used also for this method to produce an image recording apparatus and an image erasing apparatus, which is advantageous.
However, when the thermoreversible recording medium has an RF-ID tag therein as described in, for example, Japanese Patent Application Laid-Open (JP-A) No. 2004-265247 and Japanese Patent (JP-B) No. 3998193, the thickness of the thermoreversible recording medium is large and the flexibility of the thermoreversible recording medium decreases. As a result, uniformly pressing the heat source requires a high pressure. Also, contacting the heat source with the recording medium scrapes off the surface of the recording medium to form concaves and convexes, when printing and erasing are performed repeatedly. Then, there are formed areas which cannot come into contact with the heat source such as a thermal head or a hot stamp, resulting in failure to uniformly heat the surface of the recording medium to cause problems such as decrease in density and erase failure (see JP-B No. 3161199 and JP-A No. 09-30118).
Since the information stored in the RF-ID tag is read and rewritten in a non-contact manner (at a distance), there has been increased desire to rewrite the image of the thermoreversible recording medium in a non-contact manner. For example, there has been proposed a method using a laser as a method for uniformly recording and erasing images in a non-contact manner or at a distance, which method is employed when the surface of the thermoreversible recording medium has convexes and concaves (see JP-A No. 2000-136022). This proposed method performs non-contact recording on thermoreversible recording media used in conveyance containers for logistics lines. And, this patent literature describes that writing is performed with a laser and erasing is performed with hot air, hot water or an infrared heater.
Such a laser recording method is performed with a laser recording apparatus (laser marker) capable of applying high-power laser beams to thermoreversible recording media and controlling the position where the laser beams are applied. This laser marker can be used to apply laser beams to a thermoreversible recording medium so that the light heat converting material in the recording medium converts light into heat which can be used to record and erase images. Hitherto, as a method for recording and erasing images using laser beams, there has been proposed a method for recording images with near-infrared laser beams using in combination a leuco dye, a reversible color developer, and various light heat converting materials (see JP-A No. 11-151856).
Using the prior arts described in JP-A Nos. 2008-62506 and 2008-213439, it is possible to uniformly heat a recording medium to improve the recording medium in image quality and durability to repeated printing. However, the time required for image recording and erasing is elongated due to jump between the drawing lines and the waiting time.
Furthermore, JP-A No. 2008-194905 discloses a method in which the surface conditions of the recording medium are detected and then the irradiation energy is controlled according to the detection. This method can print high-quality images even on fine convexes and concaves by controlling the irradiation energy. However, it requires high-precise control and poses a problem in that the cost required for the apparatus becomes too high to be employed practically.
JP-A No. 2008-68312 discloses a method in which the position of a recording medium is detected and then the position of a lens is controlled according to the detection result so that the diameter of the irradiation spot becomes constant. However, the lens system for controlling the irradiation spot diameter is complicated to problematically elevate the cost required for the apparatus.
So far, there has not yet been provided an image processing method and an image processing apparatus which measure the distance between the image processing apparatus and the medium and control the irradiation energy of laser beams based on the measured distance, thereby performing high-quality image recording with less faint printing and bleeding, exhibiting improved durability to repeated printing, being low cost, and exhibiting high processing speed.